Acoustic diaphragm



W. H. DAVIS AND F. E. 1088.

ACOUSTIC DIAPHRAGM. APPLICATION FILED MAY 1a, 1918.

1,389,632. Patented Sept. 6,1921.

UNITED STATES PATENT OFFICE.

WILLIAM. H. DAVIS, OF BRONXVIILE, AND FREDRICK E. JOSS, OF BROOKLYN, NEW YORK, ASSIGNORS '10 LEKTOPHONE CORPORATION, A CORPORATION OF DELA- WARE.

acous'rrc ornament To all whom it may concem:

Be it known that we, WILLIAM H. DAVIS and FREDRICK E.- Joss, both citizens of the -United States, residing at, respectively,

Bronxville, county of Westchester, State of New York and borough of Brookl n, county of kings, city and State of ew York, have invented certain new and useful Improvements in Acoustic Diaphragms;

and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to acoustic diahragms, and in particular to diaphragms of the type which, while capable of use in other and different apparatus and for different purposes, are designed primarily for installation in talking machines of the general character disclosed in the patent to Marcus C. Hopkins No. 1,271,527.

According to the disclosure in said application, the diaphragm is of such a nature as to effect the direct propagation, in free air,

from a record or equivalent element .subjected to the action of the original sound waves or vibrations, of self-sustaining sound waves substantially corresponding in intensity and amplitude, as well as in pitch and timbre to the said original sound waves, as distinguished from an initial generation of violent air disturbancesin a small, confined space, and a subsequent transformation of such disturbances into self-sustaining sound waves by means of a megaphone, horn or like amplifier. The dia hragm is of relatively great area and o conical form, terminating at its base in a supporting rim or flange, and is rigidly mounted at its said rim; the shocks or vibrations being transmitted, by suitable means or devices, to the diaphragm in the direction of its apex, so that the entire conical portion is caused to move bodily.

The object of improve a the present invention is to diaphragm of this character, by

so constructing it as to reduce to a very' large degree,

if not entirely, the. possible distortion of the viglorations traismitted to or imparted by t e iaphra ue in part to the direct and rather rig ii i izonnection of the base of the cone to the supporting rim or flange, (which has the efiect of somewhat damping the vibrations), and, in part, to-

Speciflcation of Letters Patent.

Appllcationflled na 'ia, 1918. Serial No. 234,104.

the cone base itself, which may, perhaps, exert a similar action, but in less degree, by reason of such connection. This object is effected by avoiding the direct connection JUST) referred to, and, instead, joining the base of the cone to the supporting rim or flange by a curved, open-topped trough, which provides a resilient mounting for the cone and is constructed and arranged in such a way as to destro distortive action due to the presence of-t e rim and at the same time to resiliently support the cone itself. The supporting rim for the outer edge of the conical diaphragm comprises a palr of concentric nesting rings, which are arranged to grip the outer edge of the conical diaphragm and support it, so'that the said outer edge is substantially vertical. The degree of resiliency that is given to the open topped trough may be regulated by clamping more or less of the outer edge of the conical diaphragm between the nested rings.

Referring now to the drawings which illustrate one embodiment of the invention, Figure l is a sectional view taken through the axis of the cone; Fig. 2 is a fragmentary sectional view showing a detail of the supporting rim and associated parts of the cone; and Fig. 3 is a front view of a detail.

Referring more particularly to said drawing, 7 indicates, generally, t e conical portion of the diaphragm, and 8 its supporting rim or flange, these two parts being separated or spaced from each other by the intermediate, open-topped annular trough 9, hereafter more fully described. The run 8 of the cone is clamped between a pair of concentric nested rin s 10 and 11, so that it is substantiall paraTlel to the axis of the cone and is su stantially vertical as seen in the drawings. The outer ring 10 is provided with a pair of terminal flanges 13 provided with cooperating threaded apertures in which an adjusting bolt 14 engages. It will be apparent that through mampulation of this bolt 14 the clamping action of the two rings may be regulated and the area of the rim 8 that is gripped: between the two rings readily adjusted. The cone 7 has socured to its apex a cap 15, preferabl consisting of two conical members locate upon opposite sides of the cone and having a threaded connection which enables them i be tightened together so as to grip the ma- 11 ness of the rim and the cone.

terial of the cone between them. Any suitable connecting device maybe employed for transmitting from therecord or its equivalent to the diaphragm, or vice Versa, the sound waves to be reproduced, or recorded, such connection being here shown as embodying a rod 16, one end of which is fastened to the afore-mentioned cap by a screw 17.

The cone, trough and rim are preferably constructed from a single piece 0 material, which should be crisp, strong and suitably rigid or stiff, yet light and vibratile, and with as little inertia as possible, hot compressed paper or other fibrous material of like character having been found to answer the purpose satisfactorily. The cap llis made of extremely light and very rigid metal.

As is apparent from Fig. 2, the wall of the trough 9 is made appreciably thinner than the wall of the cone itself and the rim 8. Thethinning of the lower portion of the cone wall may be so carried out that said wall is gradually and inappreciably increased in thickness as it rises from the trough until a point is reached which is at some considerable height above said trough. This thinning of the trough (and of the cone wall if adopted) is effected after the diaphragm has been. formed, and constitutes an important feature of the invention, since because of it the resilience of the trough with relation to the rim is increased beyond the normal, so that the cone is rendered responsive to virtually the maximum degree to the vibrations imparted to it and is enabled to move sharply and bodily at each vibration, while returning, or tending to return, to its normal position immediately at the conclusion of its movement in one direction, this being due to the crisp, resilient nature of the material of which the diaphragm is made. The normal resilienceabove referred to is intended to indicate the degree of resilience which the trough would possess if its thickness were constant throughout and were the same as the Consequently, the distortion to which the sound waves would otherwise be subjected, is avoided,

thickowing to the removal of the damping action exerted by the rim upon the vibrations, as has already been explained. The resiliency imparted to the vibrating cone is regulated by clamping more or less of the rim 8 of the cone between the nested rings 10 and 11. Thus, when the rim is inserted to its full, or nearly its full, extent between the rings, the trough is brought closer to the bottom of said rings and is, in consequence, held more rigidly than is the case when only a comparatively small ortion of the rim lies between the rings. extent of the exposed portion of the rim is such as to allow the trough relatively great freedom of movement, and the resiliency of the mount is proportionately increased.

We claim:

1. An acoustic diaphragm, comprising a central, vibratile cone, an annular support ing rim encircling said cone 6:? the Lass thereof, and an annular trough between said cone and said rim and providin; a resilient mounting for the former; and a support for said diaphragm comprising a pair of nested rings between which said rim may be in serted to different extents to vary the resiliency of said trough with relation to said rim.

2. An acoustic diaphragm, com rising a central, vibratile cone, an upstanding supporting rim encircling said cone at the base thereof, and an annular trough connecting the lower portion of said rim and said cone base and providing a resilient mounting for the cone; and a support for said diaphragm comprising a pair of nested rings between which said rim is rigidly held.

. 3. An acoustic diaphragm, comprising a central, vibratile cone, an annular supporting rim encircling said cone at the base thereof, and an annular trough between said cone and said rim and providing a resilient mounting for the former; a support for said diaphragm comprising av pair of nested rings between which said rim is inserted; and means providing for a relative adjustment between said rim and said rings, to vary the degree of resilience of the mounting.

WILLIAM H. DAVIS. FREDRICK E. JOSS.

n the latter case, the I 

